Contact and housing having means for establishing a moisture-proof seal therebetween



Feb. 22, 1966 5, TERRY 3,236,988

- CONTACT AND HOUSING HAVING MEANS FOR ESTABLISHING A MOISTURE-PROOF SEAL THEREBETWEEN Filed Nov. 5, 1964 INVENTOR. J/zn zzz 259W Jim/V1576" United States Patent CONTACT AND HOUSIING HAVING MEANS FOR ESTABLHSEHNG A MOIST URE-PROOF SEAL THEREHEETWEEN Stanley M. Terry, Longmeadow, Mass., assignor to R. E.

Phelon (30., inc, East Longmeadow, Mass, a corporation of Massachusetts Filed Nov. 3, 1964, Ser. No. 408,516 Claims. (Cl. 200-166) This invention relates to improvements in solenoidoperated electric switches and deals more particularly with improvements in solenoid switches of the type used to control the electrical starter circuits for internal combustion engines.

The solenoid-operated switch shown in this application is similar in many respects to the one described in my pending application Serial No. 169,272, filed January 29, 1962, and reference is made to said application for a more detailed description of the construction and operation of such a switch.

Switches of the type with which this invention is concerned are designed to be used in the circuit between the battery and the starter of an internal combustion engine. Housings for better quality switches of this type are usually sealed against moisture to combat oxidation and corrosion of the contacts, the solenoid wire and other working parts contained in each housing. To maintain such a seal it has heretofore been customary to provide special sealing lock washers on terminal studs which pass through apertures in the housing. Customarily the enlarged heads of two terminal studs form the main stationary switch contacts which carry the heavy starting current load, and the contact surfaces on these stud heads are usually machined after the studs are tightly assembled with the housing to insure that the two contact surfaces thereof are located in the same plane, thereby enabling the moving contact washer to seat flatly on both of said contact surfaces simultaneously. Nuts acting in conjunction with the sealing lock washers are used to secure these two terminal studs in the switch housing and are tightened on the respective terminal studs before the contact surfaces are machined on the stud heads. In service, an additional nut is used on each terminal stud to connect thereto an appropriate battery or starter cable. When this latter nut is loosened or tightened to remove or connect the associated cable the other nut is often loosened or for some other reason often fails to hold the stud from turning, with the result that the stud is turned to bring its contact surface out of alignment with that of the other stud.

The general object of this invention is to provide a solenoid-operated switch construction which in comparison to present switches of the same general type omits parts and is of lower manufacturing cost, while nevertheless exhibiting qualities the same as or better than such present switches.

Another object of this invention is to provide an improved means for establishing a moisture-proof seal between a terminal stud and the housing of a solenoidoperated switch.

A more particular object of this invention is to provide an improved means for connecting a terminal stud to the housing of a solenoid-operated switch, which means eliminates the necessity for providing sealing lock washers on the terminal studs, with resulting reductions in switch manufacturing cost.

A further object of this invention is to provide an improved means for connecting a terminal stud to the housing of a solenoid-operated switch so that the stud will be securely held against rotation relative to the housing to reduce the possibility of the stud being rotated in attaching or removing a cable or lead to or from the stud.

A still further object of the invention is to provide a means for effecting a moisture-proof seal adjacent a stud receiving aperture in a switch housing despite the presence of a rough or chipped edge at either end of the aperture.

Other objects and advantages will be apparent from the following description and from the drawings forming a part hereof.

The drawing shows a preferred embodiment of the invention and such embodiment will be described, but it will be understood that various changes may be made from the construction disclosed, and that the drawing and description are not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

Of the drawing:

FIG. 1 is a longitudinal sectional view of a solenoid switch embodying the present invention.

FIG. 2 is a view taken generally along the line 22 of FIG. 1, the end cover and the plunger assembly having been omitted from this view to show more clearly the construction of other parts of the switch.

FIG. 3 is an enlarged side elevational view of a terminal stud employed in the switch of FIG. 1.

FIG. 4 is an end view of the terminal stud of FIG. 3.

FIG. 5 is a fragmentary sectional view showing one of the terminal studs of FIG. 1 in one phase of its assembly with the associated housing.

Turning now to the drawing, FIGS. 1 and 2 show a solenoid switch 10 incorporating the present invention. This switch has a generally conventional appearance and includes a housing 12, an end cover 14, two large stationary terminal studs 16, 16, two smaller terminal studs 20, 20, a solenoid coil means, and a plunger assembly. The housing 12 is preferably made from a molded plastic, such as a phenolic resin, and as shown consists of a hollow generally cylindrical body closed, except for a central aperture, at its lower end and open at its upper end, the upper end including a generally radially outwardly extending flange which receives the end cover 14. The end cover is in turn secured to the housing flange by rivets, screws or other conventional means.

The solenoid coil means includes a solenoid coil 24, made of many turns of wire, positioned in the lower part of the housing 12, and wound on a bobbin 26 of nylon or equivalent electrical insulating material having a centrally located and axially extending cylindrical bore 28. Surrounding the coil and bobbin is a ferromagnetic shield 30 and interposed between the bottom face of the bobbin 26 and the lower wall of the housing 12 is a ferromagnetic bottom washer 32. This washer is held to the housing 12 by a means of a nose pin 34 which passes through the washer, the aperture in the bottom of the housing, and an aperture in an associated mounting bracket 36 for attaching the switch to various diiferent supporting structures. The lower end of the nose pin 34 is staked over against the lower face of the bracket 36, as shown in FIG. 1, so that the washer, housing and bracket are held thereby in tightly assembled relationship.

Adjacent the upper face of the bobbin 26 is another ferromagnetic washer 38 and a washer-shaped electrical insulating bobbin lock 40. Both of these latter two members are centrally apertured, and the bobbin on its upper face includes a short axially extending portion or chimney 42 which passes through the apertures so that the bore which receives the plunger is comprised entirely of the bobbin bore 28.

The two large terminal studs 16, 16 extend transversely through apertures in the side wall of the housing 12 at diametrically opposite locations, and each at its inner end provides a stationary contact for cooperation with the contact washer, hereinafter described, of the plunger assembly. More particularly, each stud includes an enlarged head 44 which is preferably, and as shown, rectangular in shape as viewed from the end of the stud. Each of these heads is in turn machined, after assembly of the studs with the housing, to provide a flat upwardly facing contact surface 48 located in a plane generally perpendicular to the axis of the bore 28 and common to the other contact surface 48. Each stud 16 further includes a cylindrical shank portion 50 adjacent the head 44 and a threaded outer end portion 52; which extends outwardly beyond the housing and which threadably receives a nut 54 for drawing the stud into a fixed position relative to the housing and for thereafter aiding in holding the stud in such position. An intermediate tapered shank portion 56 of circular cross-section connects the threaded outer end portion 52 with the cylindrical shank portion 50, the threaded end portion 52 having a major diameter smaller than the diameter of the cylindrical shank portion 50. The major diameter of the tapered shank portion 56 is equal to the diameter of the cylindrical shank portion 50 and its minor diameter is substantially equal to the major diameter of the threaded outer end portion 52.

Referring to FIG. 5, which shows one terminal stud 16 in one phase of its assembly with the associated housing 12, the wall of the housing 12 is drilled or otherwise machined or formed to provide a transverse cylindrical aperture 58 for each terminal stud. Each of these apertures has such a diameter as to produce a clearance fit with respect to the threaded outer end portion 52 of the associated terminal stud and an interference fit with the cylindrical shank portion 50 Also, the length of the aperture 58 is substantially greater than the combined length of the tapered shank portion 56 and the cylindrical shank portion 50 of the associated stud 16, so that from the outside of the housing the threads of the stud extend all the way up to and slightly beyond its outer surface. Various different tolerances may be applied to the interference fit between the housing and the studs depending on what material is used for the housing and on the nominal diameter of the studs. Regardless of these factors the minimum interference is always preferably at least one thousand of an inch; the maximum interference, on the other hand, is that which may safely be used without danger of cracking the housing. With a housing made of a high impact phenolic molding compound and a five-sixteenth inch nominal diameter stud, for example, interferences of as high as twenty-four thousandths of an inch have been repeatedly used without cracking the housing, but for safety the maximum acceptable interference is preferably limited to about twelve thousandths of an inch. For smaller diameter studs the maximum acceptable interference should be reduced from this value while for larger diameter studs it may be increased.

Referring again to FIG. 5, it will further be noted that each housing aperture 58 is so located with respect to the solenoid coil and its associated parts that when a terminal stud 16 is inserted in the aperture one elongated side 59 of the stud head will lie close to the bobbin lock 40, and when a nut 54 is threaded onto the outer end portion of the stud the torque applied to the stud will tend to rotate the stud head and cause it to bear firmly against the bobbin lock securely to hold the solenoid coil and its associated parts in place in the housing and also to prevent the stud from turning during the tightening of the nut.

In assembling a stud 16 in a housing aperture 58, as the associated nut 54 is tightened on the stud the tapered shank 56 and the cylindrical shank 50 are drawn into the aperture 58, and they deform the aperture to cause it to conform with and to tightly frictionally grip these shank portions to provide the desired seal between the housing and the stud. Actually, the sealing engagement takes place within the aperture bore between the surface of the aperture bore and the surface of the stud portions 50 and 56, and therefore the finish of the edge surfaces at either end of the aperture is not critical. Minor chipping at these edges, as often occurs incidental to the drilling of an aperture, will accordingly not destroy the integrity of the seal as it usually does in other present switch designs.

As mentioned, an additional nut, not shown, is normally thread-ed onto the outer end portion of each terminal stud 16 to secure thereto an appropriate battery or starter cable. Loosening or tightening of this nut to remove or connect the associated cable often in prior switches results in an inadvertent turning of the associated terminal stud or a loosening of the nut 54, which latter happening in turn loosens the stud relative to the housing to permit it eventually to be turned by other forces. The combination of the present invention overcomes this difficulty insofar as suificient frictional restraint is obtained by the interference between the terminal studs and the housing that the studs will normally resist turning in the housing as a result of the application of torque sufficient to loosen or tighten the associated cable retaining nuts. Also, the illustrated switch construction eliminates the need for terminal sealing washers, while improving the moisture sealing qualities of the switch, thereby making possible the provision of a switch of quality equal to or exceeding that of previous switches at a lower production cost,

Also included in the switch 10 is a plunger 60 which cooperates with the coil 28 and is reciprocated axially in response to the energization and de-energization of the latter. The lower portion of the plunger 60 is received by the upper portion of the coil bore 28. The upper end of the plunger 60 includes a stem 62 which is received in the guide bore 64 formed in the end cover 14-. The plunger 60 is cylindrical in shape and has end diameters closely conforming to those of the associated receiving bores. It will therefore be seen that the plunger is slidably supported at both of its ends so as to be guided for motion in a straight axial path.

Secured in assembly on the plunger 60 by an intermediate insulating grommet 68 is a contact washer 66 which is adapted to simultaneously contact both of the fixed contacts 48, 43 and make electrical connection therebetween when the plunger is activated by energ-ization of the coil 28 and be out of contact with the same contacts 48, 48 when the plunger is in its unactivated position. The contact washer 66 also cooperates with an auxiliary spring contact associated with one of the terminal studs 24), 26 to make electrical switching contact therewith.

It should further be noted that the housing and stud combination described above need not apply only to the main fixed terminal studs 16, 16, but may also be utilized in connection with other studs passing through the housing. For example, in FIG. 2 the features disclosed with regard to the terminal stud 16 and its associated housing aperture 53 are also included in the terminal studs 20, 20 and their respectively associated housing apertures. The terminal studs 20, 20 differ from the studs 16, 16 only in size and in the shape of their enlarged head portions. One of the studs 20, 29 serves to make an electrical connection with the solenoid coil 24. The other serves to make an electrical connection with the aforementioned associated auxiliary spring contact. For a more detailed description of the function of these two terminals, reference is made to my aforementioned pending patent application.

The invention claimed is:

u 1. In a solenoid operated electric switch the combinatron of a terminal stud with a switch housing; said stud having an enlarged head located inside of said housing and defining a stationary contact surface, a cylindrical shank portion adjacent said head, a threaded outer end portion with a major diameter smaller than the diameter of said cylindrical shank portion, and a tapered shank portion intermediate said outer end portion and said cylindrical shank portion; said housing having a wall with a cylindrical aperture through which said stud passes and adjacent said aperture having an interference fit with said cylindrical shank portion of said stud.

2. The combination defined in claim 1 further characterized by said housing being molded from a high impact phenolic molding compound and said cylindrical shank portion prior to assembly with said housing having a diameter at least one thousandths of an inch greater than the diameter of said cylindrical aperture.

3. The combination defined in claim 1 further characterized by said cylindrical aperture having an axial length substantially greater than the combined axial length of said tapered shank portion and said cylindrical shank portion.

4. In a solenoid operated electric switch the combination comrising a housing, a solenoid coil positioned in said housing and having a central axially extending bore, a plunger slidably received by said coil bore for axial reciprocating movement relative to said coil between actuated and unactuated positions in response to energization and de-energization of said coil, a contact washer carried by said plunger and extending radially outwardly therefrom, and two terminal studs spaced circumaxially of said axis of said plunger and extending transversely through said housing, each of said studs having an enlarged head providing a contact surface facing said contact washer and having a cylindrical shank portion adjacent said head, each of said studs further having a threaded outer end portion with a major diameter smaller than the diameter of said cylindrical shank portion and a tapered shank portion intermediate said cylindrical shank portion and said threaded outer end portion, said housing having a wall with two cylindrical apertures passing transversely therethrough for receiving said studs, each of said apertures in said housing wall prior to assembly with the associated stud having a diameter smaller than the diameter of the cylndrical shank portion of said associated stud and larger than the major diameter of the threaded outer end portion thereof, so that when each stud is assembled with said housing its cylindrical shank portion deforms said housing to provide a tight sealing engagement between said housing and the surface of said cylindrical shank portion.

5. In a solenoid operated electric switch the combination of a terminal stud with a switch housing; said stud having an enlarged head located inside of said housing, a cylindrical shank portion adjacent said head, a threaded outer end portion with a major diameter smaller than the diameter of said cylindrical shank portion, and a tapered shank portion intermediate said outer end portion and said cylindrical shank portion; said housing having a wall with a cylindrical aperture through which said stud passes and adjacent said aperture having an interference fit with said cylindrical shank portion of said stud.

N 0 references cited.

KATHLEEN H. CLAFFY, Primary Examiner.

H. O. JONES, Assistant Examiner. 

1. IN A SOLENOID OPERATED ELECTRIC SWITCH THE COMBINATION OF A TERMINAL STUD WITH A SWITCH HOUSING; SAID STUD HAVING AN ENLARGED HEAD LOCATED INSIDE OF SAID HOUSING AND DEFINING A STATIONARY CONTACT SURFACE, A CYLINDRICAL SHANK PORTION ADJACENT SAID HEAD, A THREADED OUTER END PORTION WITH A MAJOR DIAMETER SMALLER THAN THE DIAMETER OF SAID CYLINDRICAL SHANK PORTION, AND A TAPERED SHANK PORTION INTERMEDIATE SAID OUTER END PORTION AND SAID CYLINDRICAL SHANK PORTION; SAID HOUSING HAVING A WALL WITH A CYLINDRICAL APERTURE THROUGH WHICH SAID STUD PASSES AND ADJACENT SAID APERTURE HAVING AN INTERFERENCE FIT WITH SAID CYLINDRICAL SHANK PORTION OF SAID STUD. 